The invention relates to a method for the manufacture of oligomeric and/or polymeric radiation-reactive precursors of polyimidazoles and polyimidazo-pyrrolones, as well as to the use of these radiation-reactive precursors.
Polyimidazoles are characterized by extraordinary chemical resistance to acids and bases, and it is known that polyimidazo-pyrrolones exhibit nearly twice the resistance to hard radiation as compared to polyimides. These special properties of the foregoing polymer types therefore appear useful in the area of generating fine structures. For this purpose, however, it is necessary that soluble radiation-reactive precursors of these polymers are available, from which fine structures can be generated by means of photolithographic processes.
Radiation-reactive polyimidazole and polyimidazopyrrolone precursors are already known (U.S. Pat. No. 4,397,999), and specifically in the form of addition products of olefinically unsaturated monoepoxides on amino group-containing polycondensation products of aromatic and/or heterocyclic tetraamino compounds with dicarboxylic-acid chlorides or esters (polyimidazole precursors) or on amino group-containing polyaddition products of the tetraamino compounds and tetracarboxylic acid dianhydrides (polyimidazo pyrrolone precursors).
The foregoing manufacturing method is not entirely satisfactory, however. Thus, purification processes are required if acid chlorides are used. In addition, the reaction of the amino group-containing polycondensation or polyaddition products requires an excess of unsaturated monoepoxide, which can occasionally lead to difficulties in the purification of the reaction products; in addition, longer reaction times may be necessary. Furthermore, the polymer precursors obtained have limited photosensitivity, obviously due to incomplete reaction and because of secondary reactions.
It is an object of the invention, therefore, to develop a method for the simple preparation of polyimidazole and polymidazo-pyrrolone precursors which are soluble in organic solvents, are at the same time radiation-reactive and are of high purity, i.e., are in particular free of chloride.